arXiv subjects

Irina Novikova

Publications and source records attributed to Irina Novikova.

At least 37 records · Page 2Linked to original sources

arXiv2020

Quantum-Enhanced Two-Photon Spectroscopy Using Two-mode Squeezed Light

We investigate the prospects of using two-mode intensity squeezed twin-beams, generated in Rb vapor, to improve the sensitivity of spectroscopic measurements by engaging two-photon Raman transitions. As a proof of principle demonstration, we demonstrated the quantum-enhanced measurements of the Rb $5D_{3/2}$ hyperfine structure with reduced requirements for the Raman pump laser power and Rb vapor number density.

physics.atom-ph↗

arXiv2020

Quantum-Limited Squeezed Light Detection with a Camera

We present a technique for squeezed light detection based on direct imaging of the displaced-squeezed-vacuum state using a CCD camera. We show that the squeezing parameter can be accurately estimated using only the first two moments of the recorded pixel-to-pixel photon fluctuation statistics, with accuracy that rivals that of the standard squeezing detection methods such as a balanced homodyne detection. Finally, we numerically simulate the camera operation, reproducing the noisy experimental results with low signal samplings and confirming the theory with high signal samplings.

quant-ph↗

arXiv2019

Measurements with prediction and retrodiction on the collective spin of 10^{11} atoms beat the standard quantum limit

Quantum probes using $N$ uncorrelated particles give a limit on the measurement sensitivity referred to as the standard quantum limit (SQL). The SQL, however, can be overcome by exploiting quantum entangled states, such as spin squeezed states. We report generation of a quantum state, that surpasses the SQL for probing of the collective spin of $10^{11}$ $\text{Rb}$ atoms contained in a vapor cell. The state is prepared and verified by sequences of stroboscopic quantum non-demolition (QND) measurements, and we apply the theory of past quantum states to obtain the spin state information from the outcomes of both earlier and later QND measurements. In this way, we obtain a conditional noise reduction of 5.6 dB, and a metrologically-relevant squeezing of $4.5\pm0.40~\text{dB}$. The past quantum state yields tighter information on the spin component than we can obtain by a conventional QND measurement. Our squeezing results are obtained with 1000 times more atoms than in any previous experiments with a corresponding record $4.6\times10^{-13} rad^2$ variance of the angular fluctuations of a squeezed collective spin.

quant-ph↗

arXiv2019

Polarization-Based Truncated SU(1,1) Interferometer based on Four-wave Mixing in Rb vapor

We propose and demonstrate a polarization-based truncated SU(1,1) interferometer that outputs the desired optical joint-quadrature of a two-mode squeezed vacuum field and allows its measurements using a single balanced homodyne detector. Using such setup we demonstrated up to $\approx$2 dB of quantum noise suppression below the shot-noise limit in intensity-difference and phase-sum joint quadratures, and confirmed entanglement between the two quantum fields. Our proposed technique results in a better balance between the two ports of the detector and, consequently, in better common noise suppression for differential measurements. As a result, we were able to observe flat joint-quadrature squeezing and entanglement at wide range of detection frequencies: from several MHz (limited by the photodiode gain bandwidth) down to a few hundred Hz (limited by electronic noises).

physics.optics↗

arXiv2018

Spatial multiplexing of squeezed light by coherence diffusion

Spatially splitting nonclassical light beams is in principle prohibited due to noise contamination during beam splitting. We propose a platform based on thermal motion of atoms to realize spatial multiplexing of squeezed light. Light channels of separate spatial modes in an anti-relaxation coated vapor cell share the same long-lived atomic coherence jointly created by all channels through the coherent diffusion of atoms which in turn enhances individual channel's nonlinear process responsible for light squeezing. Consequently, it behaves as squeezed light in one optical channel transferring to other distant channels even with laser powers below the threshold for squeezed light generation. An array of squeezed light beams was created with low laser power $\sim\text{mW}$. This approach holds great promise for applications in multi-node quantum network and quantum enhanced technologies such as quantum imaging and sensing.

quant-ph↗

arXiv2018

Quantized Nonlinear Gaussian-Beam Dynamics $-$ Tailoring Multimode Squeezed-Light Generation

We present a general, second quantization procedure for multi-transverse-spatial mode Gaussian beam dynamics in nonlinear interactions. Previous treatments have focused on the spectral density and angular distribution of spatial modes. Here we go a layer deeper by investigating the complex transverse-spatial mode in each angular-spatial mode. Furthermore, to implement the theory, we simulate four-wave mixing and parametric down-conversion schemes, showing how one can elucidate and tailor the underlying multi-transverse-spatial mode structure along with it's quantum properties.

quant-ph↗

arXiv2018

An analytically simple and computationally efficient Gaussian beam mode-decomposition approach to classical diffraction theory

We present a method of Gaussian-beam-mode decomposition to calculate classical diffraction of optical beams by apertures. This method offers a entirely different approach to examine the classic problem. Although our method is based on a very straightforward setup, it is surprisingly effective. We validate our method by comparing its results with those of Kirchhoff's full diffraction formula. Not only does our method have a simple and organized analytical framework, it also offers significant computational advantage.

physics.optics↗

arXiv2018

Optical Angular Momentum Manipulations in a Four Wave Mixing Process

We investigate the spatial and quantum intensity correlations between the probe and Stokes optical fields produced via four-wave mixing in a double-Λ configuration, when both incoming probe and control fields carry non-zero optical orbital angular momentum (OAM). We observed that the topological charge of the generated Stokes field obeyed the OAM conservation law. However, the maximum values and optimal conditions for the intensity squeezing between the probe and Stokes fields were largely independent of the angular momenta of the beams, even when these two fields had significantly different OAM charges. We also investigated the case of a composite-vortex pump field, containing two closely-positioned optical vortices, and showed that the generated Stokes field carried the OAM corresponding to the total topological charge of the pump field, further expanding the range of possible OAM manipulation techniques.

physics.optics↗

arXiv2018

Transit Ramsey EIT resonances in a Rb vacuum cell

We investigate a dual-channel arrangement for electromagnetically-induced transparency in a vacuum Rb vapor cell, and report the observation of a transient spectral feature due to the atoms traversing both beams while preserving their ground-state spin coherence. Despite a relatively small fraction of atoms participating in this process, their contribution to the overall lineshape is not negligible. By adjusting the path difference between the two optical beams, the differential intensity measurement can produce an error signal for the microwave frequency stabilization as strong as a single-channel measurement, but it provides a much higher signal-to-noise ratio due to the cancellation of intensity noise, dominating the signal channel detection.

physics.atom-ph↗

arXiv2018

Comparison of collimated blue light generation in ${}^{85}$Rb atoms via the D${}_1$ and D${}_2$ lines

We experimentally studied the characteristics of the collimated blue light (CBL) produced in ${}^{85}$Rb vapor by two resonant laser fields exciting atoms into the $5D_{3/2}$ state, using either the $5P_{1/2}$ or the $5P_{3/2}$ intermediate state. We compared the CBL output at different values of frequency detunings, powers, and polarizations of the pump lasers in these two cases, and confirmed the observed trends using a simple theoretical model. We also demonstrated that the addition of the repump laser, preventing the accumulation of atomic population in the uncoupled hyperfine ground state, resulted in nearly an order of magnitude increase in CBL power output. Overall, we found that the $5S_{1/2} - 5P_{1/2} - 5D_{3/2}$ excitation pathway results in stronger CBL generation, as we detected up to $4.25~μ$W using two pumps of the same linear polarization. The optimum CBL output for the $5S_{1/2} - 5P_{3/2} - 5D_{3/2}$ excitation pathway required the two pump lasers to have the same circular polarization, but resulted only in a maximum CBL power of $450$~nW.

physics.atom-ph↗

arXiv2017

Characterization of frequency stability in EIT-based atomic clocks using a differential detection scheme

We investigate a recently proposed scheme for differential detection of the magneto-optical rotation effect and its application to electromagnetically induced transparency (EIT) atomic clocks. This scheme utilizes a linearly polarized bichromatic laser field that is EIT-resonant with alkali atoms. The results of our study reveal that the suppression of the laser noise can substantially improve the signal-to-noise ratio in EIT atomic clocks. Our preliminary results demonstrate an order of magnitude improvement in clock stability under some conditions when incorporating the differential detection scheme

physics.ins-det↗

arXiv2017

Suppression of Four-Wave Mixing in Hot Rubidium Vapor Using Ladder Scheme Raman Absorption

We experimentally investigate the effectiveness of the four-wave mixing suppression in a double-lambda interaction scheme by introducing an additional ladder-type two-photon Raman absorption resonance for one of the optical fields. We propose several possible interaction configurations involving either one or two isotopes of Rb, and experimentally demonstrate the possibility of efficient four-wave mixing suppression in both EIT and far-detuned Raman cases.

physics.optics↗

arXiv2017

Multi-pass configuration for Improved Squeezed Vacuum Generation in Hot Rb Vapor

We study a squeezed vacuum field generated in hot Rb vapor via the polarization self-rotation effect. Our previous experiments showed that the amount of observed squeezing may be limited by the contamination of the squeezed vacuum output with higher-order spatial modes, also generated inside the cell. Here, we demonstrate that the squeezing can be improved by making the light interact several times with a less dense atomic ensemble. With optimization of some parameters we can achieve up to -2.6 dB of squeezing in the multi-pass case, which is 0.6 dB improvement compared to the single-pass experimental configuration. Our results show that other than the optical depth of the medium, the spatial mode structure and cell configuration also affect the squeezing level.

physics.atom-ph↗

arXiv2017

Tailorable Dispersion in a Four-Wave Mixing Laser

We present experimental results demonstrating controllable dispersion in a ring laser by monitoring the lasing-frequency response to cavity-length variations. Pumping on an N-type level configuration in ${}^{87}$Rb, we tailor the intra-cavity dispersion slope by varying experimental parameters such as pump-laser frequency, atomic density, and pump power. As a result, we can tune the pulling factor (PF), i.e. the ratio of the laser frequency shift to the empty cavity frequency shift, of our laser by more than an order of magnitude.

physics.atom-ph↗

arXiv2017

Gaussian Beam-Propagation Theory for Nonlinear Optics - Featuring an Exact Treatment of Orbital Angular Momentum Transfer

We present a general, Gaussian spatial mode propagation formalism for describing the generation of higher order multi-spatial-mode beams generated during nonlinear interactions. Furthermore, to implement the theory, we simulate optical angular momentum transfer interactions, and show how one can optimize the interaction to reduce the undesired modes. Past theoretical treatments of this problem have often been phenomenological, at best. Here we present an exact solution for the single-pass no-cavity regime, in which the the nonlinear interaction is not overly strong. We apply our theory to two experiments, with very good agreement, and give examples of several more configurations, easily tested in the laboratory.

physics.optics↗

arXiv2017

Why a hole is like a beam splitter--a general diffraction theory for multimode quantum states of light

Within the second-quantization framework, we develop a formalism for describing a spatially multimode optical field diffracted through a spatial mask and show that this process can be described as an effective interaction between various spatial modes. We demonstrate a method to calculate the quantum state in the diffracted optical field for any given quantum state in the incident field. Using numerical simulations, we also show that with single-mode squeezed-vacuum state input, the prediction of our theory is in qualitative agreement with our experimental data. We also give several additional examples of how the theory works, for various quantum input states, which may be easily tested in the lab; including two single-mode squeezed vacuums, single- and two-photon inputs, where we show the diffraction process produces two-mode squeezed vacuum, number-path entanglement and a Hong-Ou-Mandel-like effect--analogous to a beam splitter.

quant-ph↗

arXiv2016

Arithmetic with optical topological charged in step-wise excited Rb vapour

We report on experimentally observed addition, subtraction and cancellation of orbital angular momentum (OAM) in the process of parametric four-wave mixing that results in frequency up- and down-converted emission in Rb vapour. Specific features of OAM transfer from resonant laser fields with different optical topological charges to the spatially and temporally coherent blue light have been considered. We have observed the conservation of OAM in nonlinear wave mixing in a wide range of experimental conditions including a non-collinear geometry of the applied laser beams and furthermore that the coherent blue light accumulates the total orbital angular momentum of the applied laser light. Spectral and power dependences of vortex and plane wave front blue light beams have been compared.

quant-ph↗

arXiv2016

Spatial Multi-Mode Structure of Atom-Generated Squeezed Light

We investigated the spatial distribution of quantum fluctuations in a squeezed vacuum field, generated via polarization self-rotation (PSR) interaction of an ensemble of Rb atoms and a strong near-resonant linearly polarized laser field. We found that the noise suppression is greatly effected by the transverse profile of a spatial mask, placed in both the squeezed field and the local oscillator, as well as its position along the focused beam near the focal point. These observations indicate the spatial multi-mode structure of the squeezed vacuum field. We have developed a theoretical model that describes the generation of higher-order Laguerre-Gauss modes as a result of PSR light-atom interaction. The prediction of this model are in a good qualitative agreement with the experimental measurements.

physics.optics↗